1. Field of the Invention
The present invention generally relates to directly injected engines. More specifically, the present invention relates to fuel injector mounting arrangements for such engines.
2. Description of Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more efficient engine emission control, better fuel economy and, at the same time, continued high power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the engine charge former. In commonly used systems, fuel is injected into an air intake manifold. This is considered indirect injection, meaning that the air-fuel charge is formed outside of the combustion chamber. To improve upon indirect injection, direct injection systems are being developed. These systems inject fuel directly into the combustion chamber for mixing with an air charge and thus have significant potential advantages, such as vastly improved emission control.
The fuel injector employed in a direct injection engine extends into a combustion chamber through an opening formed in the cylinder head assembly. The cylinder head assembly often is formed by casting. As is known, internal air pockets are typically formed within cast components. When forming the opening through which the fuel injector extends, as well as when forming a seat for sealing the fuel injector in its position, these air pockets are often uncovered. The air pockets result in reduced sealability of the assembly, thereby creating the possibility of leakage from the combustion chamber. This leakage is disadvantageous in that a portion of the air-fuel charge may be lost during each combustion stroke. In addition, high amounts of heat energy tend to escape and further degrade the seal between the components.
Additionally, in the conventional mounting arrangement, the fuel injector nozzle extends directly into the combustion chamber and is in direct contact with the high heat caused by the combustion of the air-fuel charge. As is known, the residual components following combustion can form carbon deposits that gum and partially occlude the fuel injector nozzle. These deposits typically form on surfaces of the injector and/or the cylinder head that are in direct contact with the combustion chamber under high heat conditions. The carbon deposits can make it difficult to remove the fuel injector when replacement is necessary. In addition, the deposits can form between the fuel injector body and the opening through which the fuel injector extends.